Which of the following is used to hasten maturity period of juvenile conifers ?

Options

A. Auxin
B. GA
C. Cytokinin
D. Ethylene

Answer

To determine which substance is used to hasten the maturity period of juvenile conifers, we can analyze each option provided:

1. **Oxin**: This plant hormone is primarily involved in regulating growth and development processes such as cell elongation and differentiation. It plays a significant role in xylem differentiation but is not specifically known for hastening maturity in conifers.

2. **Gibberellin (GA)**: This hormone is known for promoting growth and development in plants. It is particularly effective in breaking dormancy and promoting early seed production. Gibberellins are widely used in horticulture to accelerate the maturation process of various plants, including juvenile conifers.

3. **Cytokinin**: This hormone is involved in cell division and growth. While it plays a role in promoting shoot development and delaying leaf senescence, it does not specifically hasten maturity in juvenile conifers.

4. **Ethylene**: This is a gaseous plant hormone that regulates various aspects of growth and development, including fruit ripening and flower wilting. However, it is not primarily associated with hastening maturity in juvenile conifers.

Based on this analysis, the correct answer is **Gibberellin (GA)**, as it is the hormone that effectively hastens the maturity period of juvenile conifers and promotes early seed production.

### Step-by-Step Solution:
1. **Identify the hormones listed**: Oxin, Gibberellin (GA), Cytokinin, Ethylene.
2. **Analyze the role of each hormone**:
- Oxin: Controls xylem differentiation.
- Gibberellin (GA): Promotes growth and early seed production.
- Cytokinin: Promotes cell division and shoot development.
- Ethylene: Regulates growth processes like ripening.
3. **Determine which hormone is associated with hastening maturity**: Gibberellin (GA) is known for this function.
4. **Conclude the answer**: The substance used to hasten the maturity period of juvenile conifers is **Gibberellin (GA)**.